The proposed research is a continuance of work concerned with blood pressure control mechanisms and in relation to behavioral stress. The ultimate objective of this research is to delineate the significance of behavioral stress in the etiology of hypertension and the development of reliable behavioral techniques for the prevention and treatment of hypertension. The proposed research consists of four interrelated problems. One concerns an evaluation in both humans and chronically prepared dogs of the relative contribution of cardiac and vasomotor activity on blood pressure changes associated with environmental stress. Previous data indicate that beta-adrenergic influences on the heart seem to exert a more profound influence, particularly on systolic blood pessure, than alpha adrenergic influence on the vasculature. Furthermore, certain qualitative aspects of stress seem more effective at evoking such beta-adrenergic influences. Work is proposed which will further evaluate these hypotheses, as well as ascertain the metabolic relevance of these cardiovascular adjustments. Another aspect of the proposed work concerns an effort to develop a hypertensive condition in a chronically prepared dog by the manipulation of cadiodynamic and hemodynamic processes with behavioral stress. A third phase of the work represents the beginnings of a possible longitudinal study with human subjects which seeks to determine whether subjects demonstrating a hyper-reactive state to various types of stressors, particularly beta-adrenergic hyper-responsiveness is indicative of an eventual hypertension. Both normotensive hyper-responsiveness and borderline hypertensive subjects will be compared to hypo-responsive normotensive using laboratory and natural stressors and with respect to the stability of their cardiovascular responsiveness. A fourth facet of the work will concern an evaluation of possible renal involvement in the etiology of hypertension in a chronically prepared dog. This work seeks first to determine any specific influence of behavioral stress on renal blood flow and then the effects of manipulating renal blood flow on cardiovascular responsiveness to behavioral stressors.